1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a field-sequential-color liquid crystal display device.
2. Description of the Prior Art
Color mixing methods in liquid crystal display devices can be divided into a space-domain color mixing method and a time-domain color mixing method. The space-domain color mixing method is widely utilized. Take a thin field transistor liquid crystal display (TFT-LCD) as an example. Each display pixel is composed of a red sub-pixel, a green sub-pixel, and a blue sub-pixel. The red sub-pixel, the green sub-pixel, and the blue sub-pixel respectively correspond to a red color filter, a green color filter, and a blue color filter. By the color mixing of the red sub-pixel, the green sub-pixel, and the blue sub-pixel of each display pixel, color displaying images can be recognized by the human visual system. The time-domain color mixing method do not require the color filter, and by means of a color sequential method, the red light, the green light, and the blue light respectively pass through the liquid crystal display panel in sequence for the color mixing. Accordingly, the human visual system can recognize the effect of the color mixing by the photogene of the human eye. As a result, a field sequential color (FSC) liquid crystal display device utilizing the time-domain color mixing method to display a colorful frame has following advantages. (1) Compared with the pixel in the conventional liquid crystal display device with the color filter being composed of a red sub-pixel, a green sub-pixel, and a blue sub-pixel, the pixel in the FSC liquid crystal display device can be reduced to improve the resolution of the liquid crystal display device, or to maintain the resolution of the liquid crystal display device with reduced cost of the thin film transistor substrate. (2) Without the color filter, the product cost of the liquid crystal display device can be reduced.
Since the FSC liquid crystal display device has no color filters, the FSC liquid crystal display device may have higher transmittance than the conventional liquid crystal display device. Accordingly, the FSC liquid crystal display device may operate in a micro reflective mode that is a condition of turning off the backlight system and being disposed in an environment with sunlight at outside. In this condition, the FSC liquid crystal display device utilizes the backlight module to reflect the sunlight to display the image, so that there is no need to dispose the reflective electrode to reflect the sunlight in the FSC liquid crystal display device. However, an energy distribution of blue-green color region is larger than the other color regions in the continuous spectrum of average sunlight D65, so that when the FSC liquid crystal display device utilizes the sunlight as a light source, that is the FSC liquid crystal display device operating in the reflective mode or the backlight system being turning off to be in the micro reflective mode, the frame easily has blue-green shift at a specific viewing angle. Through actually measurement, the color shift is more obvious when the FSC liquid crystal display device is displaying the frame with high gray level. That means the optical compensation bend liquid crystal display device easily displays the frame with color shift in the condition of the liquid crystal molecules being substantially parallel to the light exit surface of the liquid crystal panel. When the viewing angle is larger in the condition of high gray level, the color shift is more serious.
Therefore, in reflective mode or micro reflective mode, to reduce the color shift of the FSC liquid crystal display device is an objective in this field when the environment light is utilized as main light source.